The present invention relates to an ink which exhibits excellent recording properties onto various media including non-ink absorptive media, a recording method using the same, an ink-jet recording method, an ink cartridge, a recording unit, and an ink-jet recording apparatus.
Conventionally employed as ink compositions (hereinafter simply referred to as ink) for ink-jet recording have widely been water-soluble liquid ink compositions. Further, a hot-melt type ink-jet recording system is proposed in which a hot-melt type ink composition, comprised of solid wax at room temperature as a component, is employed; is liquefied by heating; is ejected by application of any kind of energy; and adhered onto a recording medium followed by being cooled and solidified so as to form recorded dots. Features of said ink are as follows. Since said ink is solid at room temperature, no staining results during handling. Further, since it is possible to minimize its evaporation amount during melting, nozzles do not clog. Further said ink exhibits the following advantages. Since said ink is solidified immediately after adhesion onto a medium, no bleeding occurs. As a result, it is possible to employ various recording media such as traditional Japanese paper, drawing paper, post cards, and plastic sheets without any pretreatment. U.S. Pat. Nos. 4,391,369 and 4,484,948 disclose ink compositions which result in desired printing quality irrespective of paper quality.
Further, Japanese Patent Publication Open to Public Inspection No. 56-93776 discloses a UV curable resin type ink composition which exhibits desired adhesion onto metal surfaces. Still further, as ink for ink-jet recording which is subjected to UV curing, U.S. Pat. No. 4,228,438 discloses an ink which is comprised of an epoxy modified acrylic resin and a urethane modified acrylic resin as binders, and pigments having a particle diameter of less than or equal to 5 xcexcm as a coloring component. Japanese Patent Publication Open to Public Inspection No. 58-32674 discloses an ink which employs a cationically polymerizable epoxy resin as a binder, and Japanese Patent Publication Open to Public Inspection No. 5-186725 describes an ink which employs water-soluble or non-water-soluble dyes. Said patents disclose ink which is easily applied to recording onto common paper as well as recycled paper.
When the ink, as described above, is employed, it becomes difficult to print onto recording media which are not ink absorptive. When special paper is employed, a large-scaled ink drying device is required. Further, problems occur in which since it is difficult to carry out fine and accurate printing due to bleeding and to obtain desired resolution, the use is limited.
It is possible to carry out high speed printing by employing hot-melt type ink, comprised of a wax. However, it has been difficult to obtain durability after printing due to low abrasion resistance. Further, a system, in which a recording composition is merely cured employing ultraviolet rays, results in an insufficient curing rate, difficulty of very fine and accurate printing due to bleeding, and limited resolution.
On the other hand, when coloring agents (colorants) are employed in an ink composition for ink-jet printing, problems occur in which separation tends to occur at a fused state. As is well known, sedimentation of particles, dispersed in a medium, varies depending upon the diameter of said particles, the viscosity of the dispersion medium, and the sedimentation time. The higher the viscosity of the dispersion medium, the less sedimentation occurs. On the other hand, when printing is carried out employing an ink-jet printer, a lower viscosity of the employed ink is suitable for highly reliable printing due to advantages for an increase in a printing rate as well as an increase in density. However, both of these characteristics conflict with each other.
An ink-jet recording system, in which organic pigments are employed as a coloring agent, exhibit many advantages, especially in lightfastness, compared to an ink-jet recording system employing dyes. As a result, the former has been applied to OA equipment, general home printers, and office printers such as facsimile machines. In addition, it is now expected that ink-jet recording is applied for interior and exterior posters, sign boards, cars, glass, decorations of walls and buildings and further onto textiles. Accordingly, it has been urgently demanded to solve each of the aforesaid problems.
From the viewpoint of the foregoing, the present invention was achieved. An object of the present invention is to provide an ink which attains marked excellence in ink stability, bleeding resistance, and stability (abrasion resistance) after printing, an ink-jet recording method, an ink cartridge, a recording unit, and an ink-jet recording apparatus.
The aforesaid object of the present invention was achieved employing the following embodiments.
1. An ink-jet ink comprising a photopolymerizable compound, a photopolymerization initiator and a colorant,
wherein the ink has a viscosity of 500 to 50,000 mPaxc2x7s at 25xc2x0 C. and a viscosity of 3 to 30 mPaxc2x7s at 80xc2x0 C.
2. The ink of item 1, wherein the colorant is a pigment.
3. An ink-jet recording method, comprising the steps of:
(a) jetting the ink of item 1 through a nozzle of an ink-jet head by heating the ink to 60 to 180xc2x0 C. onto an image recording medium having a temperature of 15 to 40xc2x0 C.; and
(b) applying an actinic ray to the image recording medium after the jetting step.
4. The ink-jet recording method of item 3,
wherein the actinic ray is a ultraviolet ray.
5. The ink-jet recording method of item 3,
wherein the ink-jet head ejects the ink by an effect of piezoelectric action.
6. The ink-jet recording method of item 3,
wherein the image recording medium is not ink-absorptive.
7. An ink cartridge comprising an ink housing section which stores the ink of item 1.
8. An ink-jet recording unit comprising an ink storing section which stores the ink of item 1 and an ink-jet head section which ejects droplets of the ink.
9. The ink-jet recording unit of item 8, wherein the ink-jet head section comprises an ink-jet head which ejects the ink by an effect of piezoelectric action of the head.
10. An ink-jet recording apparatus comprising the ink cartridge of item 7, wherein recording is carried out by adhering ink droplets formed by an ink-jet system onto an ink-jet recording medium.
11. An ink-jet recording apparatus comprising the ink-jet recording unit of item 8, wherein recording is carried out by jetting the ink onto an ink-jet recording medium.
12. The ink-jet recording apparatus of item 11,
wherein the apparatus comprises a means for irradiating ultraviolet rays onto the ink-jet recording medium.
13. The ink-jet ink of item 1, wherein the ink has a surface tension of 20 to 60 mN/m.
14. The ink-jet ink of item 13, wherein the colorant is a pigment and the content of the pigment is 0.5 to 30 weight % of the ink.
15. The ink-jet ink of item 13, wherein the colorant is dispersed in a vehicle and has an average particle size of not more than 200 nm.
16. The ink-jet ink of item 13, wherein the ink-jet ink comprises at least two kinds of photopolymerizable compounds having a different number of photopolymerizable groups.
17. The ink-jet ink of item 16, wherein a weight ratio of a photopolymerizable compound having one photopolymerizable group to photopolymerizable compounds having a plurality of photopolymerizable groups is 0:100 to 50:50.
18. The ink-jet ink of item 13, wherein the ink-jet ink has a pH value of 4 to 10.
20. An ink-jet recording method, comprising the steps of:
(a) jetting the ink of item 13 through a nozzle of an ink-jet head by heating the ink to 60 to 180xc2x0 C. onto an image recording medium having a temperature of 15 to 40xc2x0 C.; and
(b) applying an actinic ray to the image recording medium after the jetting step.
21. The ink-jet recording method of item 20,
wherein the actinic ray is a ultraviolet ray.
22. The ink-jet recording method of item 20,
wherein the ink-jet head ejects the ink by an effect of piezoelectric action.
23. The ink-jet recording method of item 20,
wherein the recording medium is not ink-absorptive.
24. The ink-jet ink of item 1, wherein the ink further comprises a cationically polymerizable compound.
25. The ink-jet ink of item 24, wherein the ink has a surface tension of 27 to 65 mN/m.
26. The ink-jet ink of item 24, wherein the colorant is a pigment.
27. The ink-jet ink of item 24, wherein the ink contains 30 to 95 weight % of the photopolymerizable compound, and the weight ratio of the photopolymerizable compound to the photopolymerizable initiator is 100:0.01 to 100:20, and the weight ratio of the photopolymerizable compound to the acid polymerizable compound is 100:5 to 100:30.
28. An ink-jet recording method, comprising the steps of:
(a) providing an image recording medium in a form of a roll;
(b) jetting the ink of item 24 through a plurality of ink-jet heads onto the image recording medium; and
(c) hardening the ink on the image recording medium by irradiation with an actinic ray or by heating.
29. The ink-jet recording method of item 28,
wherein the image recording medium is not ink-absorptive.
30. The ink-jet recording method of item 28,
wherein a contact angle of the ink jetted onto the recording medium is in a rang of 20 to 70xc2x0 at 25xc2x0 C.
31. The ink-jet recording method of item 28,
wherein a surface of the recording medium is heated to 10 to 30xc2x0 C. during the jetting step of the ink.
32. The ink-jet recording method of item 31,
wherein the temperature of the surface of the recording medium is regulated based on the amount of data contained in one sheet which is to be recorded.
33. An ink-jet recording method, comprising the steps of:
(a) jetting the ink of item 1 through a nozzle of an ink-jet head by heating the ink to 60 to 180xc2x0 C. onto an image recording medium having the temperature of 15 to 40xc2x0 C.; and
(b) applying an actinic ray to the image recording medium after the jetting step,
wherein the ink contains no wax.
34. The ink-jet recording method of item 33,
wherein the temperature of the surface of the recording medium is regulated based on the amount of data contained in one sheet which is to be recorded.
35. The ink-jet recording method of item 33,
wherein the recording medium is not ink-absorptive.
36. The ink-jet recording method of item 33,
wherein a contact angle of the ink jetted onto the recording medium is in a rang of 20 to 70xc2x0 at 25xc2x0 C.
The inventors of the present invention conducted diligent investigations to overcome the aforesaid problems. As a result, the following was discovered. By adjusting the viscosity of ink, comprising at least a photopolymerizable compound, a photopolymerization initiator and a coloring agent, to 500 to 50,000 mPaxc2x7s at 25xc2x0 C. as well as to 3 to 30 mPaxc2x7s at 80xc2x0 C., it was possible to carry out high speed recording in the same manner as for hot-melt type ink employing wax. Further, poor abrasion resistance, which had been problematic in the use of said hot-melt type ink, was markedly improved. In a method which cured an ink composition merely employing ultraviolet rays, it was difficult to minimize bleeding. However, the constitution of the present invention markedly minimized bleeding, especially bleeding which occurred when non-ink absorptive recording media were employed. Accordingly, the present invention was achieved.